1. Field of the Invention
The present invention relates to a beading apparatus for attaching beadings to parts of an electron gun.
2. Description of the Related Art
In an electron gun for a cathode-ray tube, dimensions, relative positions and intervals of respective grids are manufactured with considerable precision in order to improve the focus function.
FIG. 4 illustrates the structure of an unipotential electron gun 10. In the electron gun 10, a support pin 11, grids 12 to 17, and a convergence plate 18 are arranged in a single row. Two long and slender beadings 20 adhere to pins 19 protruding from the sides of the respective parts 11 to 18. The beadings 20 hold the parts 11 to 18 firmly together.
In assembling the electron gun 10, as shown in FIG. 5, the parts 11 to 18 are placed onto supports 21 which are set on top of a support base 2 for the beading apparatus 1. A first spacer 22, a second spacer 23, and a third spacer 24, which have a predetermined thickness, protrude from the support base 2. The first spacer 22 is inserted between GM grid 14 and G3 grid 15, the second spacer 23 is inserted between G3 grid 15 and G4 grid 16, and the third spacer 24 is inserted between G4 grid 16 and G5 grid 17. Accordingly, the parts 11 to 18 can be fixed at predetermined intervals.
Further, a stabilizing lever 3 is mounted on one of two legs 25 rotatably by shaft 32. When pushed down, the stabilizing lever 3 is fixed by a clamp 4 mounted on the other leg 25 rotatably by shaft 41. The G5 grid 17 is fixed by holders 31 set on the lower side of the stabilizing lever 3 in connection with the supports 21 on the support base 2. Each of the parts 11 to 16 are held firmly in their proper positions but may be slided. Thereafter an appropriate pressing means (not shown) presses the support pin 11 in the direction of the G5 grid 17. With this, parts 11 to 18 of the electron gun 10 are firmly manufactured at predetermined intervals.
As shown in FIG. 6, two guide holes 61, being diametrically opposite each other, are perforated from the support pin 11 to the G3A grid 15A for adjusting the positions of the parts. Two adjuster pins 5 are inserted into the guide holes 61 through the parts, so that the positions of the parts 11 to 15 are adjusted on opposite sides and three beam holes 62, perforated from the G1 grid 12 to the G3 grid 15A, coincide respectively. Therefore the electron gun 10 can emit three lines of electron beams precisely at a target.
After the insertion of the adjuster pins 5, two beadings 20 are attached to the pins 19 for the parts 11 to 18. The beadings 20 combine the parts 11 to 18 in proper position and at predetermined intervals. Thereafter, the assembled electron gun 10 is removed from the support base 2, and the adjuster pins 5 are pulled out. At this point the assemblage of the electron gun 10 is completed.
In this case, for manufacturing reasons, G3A grid 15A and G3B grid 15B are manufactured separately, and, are welded together as the G3 grid 15. The G3A grid 15A is formed into a flat plate, and as shown in FIG. 6, has the guide hole 61 for adjustment of the position diametrically and the beam hole 62 for electron beam to pass through. The G3B grid 15B is formed into a cylindrical shape.
In the beading apparatus 1 for the electron gun 10 described above, the supports 21, on which the G3 grid 15 is placed, hold the whole G3B grid 15B. Therefore, in the event the G3A grid 15A and the G3B grid 15B are welded together out of position, when the G3 grid 15 is placed on the supports 21, both the guide hole 61 and the beam hole 62 of the G3A grid 15A are also out of position.
Large discordance of the guide holes 61 inhibits the adjuster pins 5 from being inserted. Small discordance, as shown in FIG. 7, may allow the adjuster pins 5 to be inserted into the guide holes 61 if the adjuster pins 5 are bent slightly. In the latter case, the beadings 20 are attached to the parts 11 to 15 on the assumption that the parts 11 to 15 are in proper position. This poor condition prevents the electron gun 10 from emitting an electron beam precisely at the target because the beam holes 62 of the G3; A grid 15A do not coincide with the beam holes 62 of the grids 12 to 14.
After the beadings 20 are attached, the discordance of the beam holes 62 of the G3A grid 15A can be corrected so as to correspond to the beam holes 62 of the grids 12 to 14 by inclining the G3 grid 15 forcibly. But the problem remains that it is difficult to adjust the position completely and that it takes a good deal of time and labor.